Zeolites, both natural and synthetic, have been employed as adsorbents for gas separation processes such as vacuum and pressure swing adsorption cycles, and for residual gas removal in vacuum thermal insulation. A zeolite ion exchanged with a precious metal has been used as an adsorbent for the removal of residual gas in vacuum operations. The zeolite is single ion exchanged and exhibits a greater adsorption capacity for ordinary atmospheric gases than common, e.g. Type X, zeolites which have not undergone ion exchange.
One type of operation in which zeolites or molecular sieves are utilized is for the separation of the gaseous components in an air stream, i.e. the separation of an air stream to form separate oxygen-rich and nitrogen-rich streams. U.S. Pat. No. 3,313,091 describes a technique whereby a Type X or Type A molecular sieve is used as an adsorbent for O.sub.2 /N.sub.2 separations from air. The molecular sieves have between 30% to 100% of their sodium cations replaced by a single divalent Group II metal cation or a monovalent silver cation. The separation process is carried out at temperatures of about 35.degree. F. to 100.degree. F. and at pressures between 1 atm and 8 atm.